BUTLER TWP — A spark from a welding torch caused material in an auto repair garage to smolder Tuesday evening before igniting into an explosive fire that destroyed the garage on McCalmont Road, authorities said. Tools, equipment, numerous auto parts and a van also went up in flames. Damage was estimated at between $300,000 and $400,000, said Butler Township fire marshal Larry Christy. The owner, John Brown, did not have insurance, fire officials said. The blaze started shortly after 6 p.m. and burned hot and heavy for about two hours before firefighters from eight departments got it under control. Soon after the fire started, at least three explosions from inside the garage startled neighbors and placed firefighters on guard. “The bangs and booms came in the first 15 minutes,” Christy said. The sources of the explosions were different fuel tanks in the garage, a 40-foot-by-50-foot pole building, fire officials said. Christy said he’s ruled the fire as accidental. Brown told investigators that he had been working with a welding torch in the garage earlier that day and had left about 30 minutes before the fire started.